Is Glyphosate Actually Safe for Bees?

Glyphosate, the active ingredient in Roundup, is the most widely used herbicide in the world. A widely cited 2016 analysis put cumulative global use at around 8.6 million tonnes between 1974 and 2014, and it’s kept climbing since, especially after “Roundup Ready” genetically modified crops arrived in 1996 and let farmers spray it directly onto growing crops.

For a long time, it was considered pretty harmless to animals. Glyphosate works by blocking a metabolic pathway that exists only in plants and some microorganisms, so the theory is that it shouldn’t affect anything with a nervous system. The more I’ve read into it, though, the less settled that “harmless” reputation looks.

The safety debate, still not settled

In 2015, the International Agency for Research on Cancer classified glyphosate as “probably carcinogenic to humans,” while the European Food Safety Authority and the US Environmental Protection Agency both concluded around the same time that it probably wasn’t. That disagreement hasn’t gone away.

A 2025 study from the Ramazzini Institute’s Global Glyphosate Study, published in the peer-reviewed journal Environmental Health, found increased rates of several tumour types in rats exposed to glyphosate from before birth, even at doses considered safe under EU limits.

Australia’s own regulator, the APVMA, reviewed the IARC finding back in 2016 and concluded glyphosate doesn’t pose a cancer risk when used according to the label, a position it’s held since while keeping an eye on new research.

Meanwhile in the US, a school groundskeeper named Dewayne Johnson became the first person to take Monsanto to trial over it. He’d sprayed Roundup as part of his job, sometimes more than 30 times a year, and was later diagnosed with terminal non-Hodgkin lymphoma, doctors gave him about two years to live. In 2018 a California jury awarded him $289 million, later reduced on appeal to $78.5 million and then $20.5 million.

His case opened the door to the thousands of Roundup lawsuits that followed, and Bayer, which makes it, proposed a multi-billion-dollar nationwide settlement in early 2026 that’s still awaiting court approval.

What glyphosate does to bees

Whatever’s true for humans, the picture for bees has gotten clearer, and more concerning, since I first wrote about this.

Back in 2018, researchers at the University of Texas at Austin found that glyphosate exposure at levels bees would actually encounter in the field measurably changed the bacteria living in honey bees’ guts.

The study, published in PNAS, found one particularly important gut bacterium dropped off after exposure, and bees with disrupted gut bacteria were more likely to die from a common infection. Bees rely on a healthy gut microbiome much the same way we do, so knocking it around isn’t a small thing.

Then in 2022, a team from the University of Konstanz and the Max Planck Institute of Animal Behavior published a study in the journal Science that I think matters more than it got credit for, because it found harm that doesn’t show up if you’re only checking whether bees are dropping dead.

They fed bumblebee colonies realistic field levels of glyphosate and found barely any difference in colony behaviour when food was plentiful and nothing was stressing the colony. But once they cut the colonies’ food supply to mimic a bad season, the glyphosate-exposed colonies lost the ability to keep their brood warm enough to develop properly, their collective ability to hold the necessary nest temperature dropped by more than 25% under resource limitation.

A healthy brood needs to stay between 25 and 35°C, and bumblebees hold it there by literally shivering their flight muscles together to generate heat. It’s a clever but energy-expensive feat for a colony, and this study found that glyphosate undermines it right when a colony needs it most.

Why this actually matters

Bumblebees like the buff-tailed bumblebee aren’t a nice-to-have; they’re specialised pollinators for crops like tomatoes, capsicums and eggplants that honey bees aren’t as good at, and species like the Arctic bumblebee can forage in conditions that would ground most other bees. They’re already under pressure from habitat loss and other pesticides.

Both studies suggest that glyphosate’s damage isn’t always the kind you’d notice by checking for dead bees; it’s quieter: a gut that can’t fight off infection as well, or a colony that can’t keep its young warm when times get tough. It’s a slow, compounding pressure that makes an already-stressed pollinator population more fragile.